1. Field of the Invention
The present invention relates to an ultrasonic applicator, and more particularly to an ultrasonic applicator for an ultrasonic-echo planigraphic imaging apparatus used when a puncturing cannula or needle is inserted into a tissue, of a living body, to be examined as in a biopsy and a blood vessel photograph method using X-ray photographing.
2. Description of the Prior Art
A biopsy examination is conducted for the purpose of picking out a tissue or a body fluid out of organs of a living body such as a liver, and a kidney by a suitable puncturing cannula or needle for medical examination. Also, a blood vessel photographing method refers to X-ray photographing by inserting the puncturing cannula into a blood vessel for injecting a contrast medium thereinto.
In such cases, if, in order to pick out a desired tissue of the living body for the medical examination or to prevent a mistake in inserting the cannula upon the injection of the contrast medium, the desired point of the living body or the blood vessel is indicated in an ultrasonic-echo planigraphical manner on a suitable indicator and the cannula is inserted thereto in accordance with the ultrasonic-echo planigraphic image, then a desired puncturing may readily be attained. Therefore, for that purpose, an ultrasonic applicator for puncturing is utilized.
For instance, as an ultrasonic applicator for puncturing, there has been often used a penetration type applicator in which a puncturing cannula guiding slot is formed substantially in the central portion of the applicator body as disclosed in U.S. Pat. No. 4,029,084 (German equivalent DE-GM No. 74 42 294).
More specifically, as shown in FIG. 1, in the prior art ultrasonic applicator puncturing probe, a number of ultrasonic transducer elements 3 are arranged parallel to one another along the length of an application surface 2 of the applicator body 1. A puncturing cannula inserting slot 4, for insertion of the cannula, through which the cannula is inserted into the tissue or the like to be examined is formed substantially in the central portion of the applicator body 1. The puncturing cannula inserting slot 4 is defined by a trapezoidal space which is tapered toward the application surface 2. A cannula guiding slot 5 for guiding the puncturing cannula into the inserting slot 4 is formed so as to penetrate from the cannula inserting slot 4 to a front surface of the applicator body 1. The ultrasonic transducer elements 3 are connected through a connector cable 6 to a suitable control means.
However, in the conventional penetration type puncturing ultrasonic applicator, since the cannula inserting slot 4 is provided in the central portion of the applicator body 1, the ultrasonic transducer elements 3 which would otherwise be provided at the opening portion of the slot 4 have been removed. As a result, the ultrasonic energy is diffused at the portion where the ultrasonic transducer elements are not provided, thereby forming an inevitable loss portion. Therefore, there would be generated a stripe-shaped defect (low brightness) on the image indicator for indicating the ultrasonic-echo planigraphic image.
In order to carry out the basic puncturing operation in which the cannula or needle is carried through a minimum distance up to a desired point of the living body to be examined, the cannula must be advanced through the stripe-shaped defect, so that it is difficult to confirm the tip end of the cannula and it is also difficult to exactly insert the cannula into the point of the living body to be examined.
Also, in the conventional applicator, since the insertion opening which is the end portion of the cannula inserting slot 4 of the ultrasonic applicator for inserting the cannula is made small at a single location, it is difficult to render the insertion opening to be aligned with the point to be examined. Furthermore, if the point to be examined is desired to be changed after the puncturing operation, it is necessary to again align the applicator to another point to be examined. The conventional applicator needs such various steps and is troublesome to handle.